It Comes Down to the Coasts: Part II

Along the seams of the earth where land meets sea, biological productivity is much higher than for the rest of the planet's surface. If the coasts are to continue serving their essential ecological and economic functions, we will have to begin altering our patterns of human settlement and development.

Synopsis of part I

The rush to the coasts is on. Every year, half of the world's vacationers head for the sea. Half the world's population live within about 50 miles of saltwater. In 30 years, the same number of people as are now on earth - 5.5 billion - are expected to live in costal zones. More than a great vacation spot, produce from the fertile coasts and rich offshore waters feed hundreds of millions of people.
By concentrating its swelling population along the coasts, humanity is locating the ecological damage of its activities precisely where the world's most productive ecosystems are concentrated. Coastal areas, which are approximately twice as productive as inland areas, suffer roughly nine times more damage because of the number of people living there.
Not all coastal habitat is highly productive: about 70 percent are lined with cliffs or ice, or are beaches with relatively low biological activity. However, wetlands and estuaries, where rivers entering the sea deposit their nutrients, are among the most productive. This makes them particularly important as nurseries for marine species, where two-thirds of all commercially caught fish spend their early life.
These naturally sheltered areas are also particularly vulnerable to damage from use and pollution. Wetlands have traditionally been considered wastelands and as targets for city expansion. For example, San Francisco Bay, the largest estuary in the western United States, has lost 60 percent of its water area to land reclamation in the past 140 years.
However, agriculture causes the most extensive destruction. The Chinese, for example, have been draining coastal wetlands for the rich soils they yield for 6,000 years. Bangladesh, with the world's highest populatiuon density for a mainland country, has impounded 30,000 square kilometers for agriculture.
Other causes of destruction include rapidly expanding fish farming, timber extraction and civil engineering pro-jects. The Mississippi River estuary is eroding at a rate of 150 square kilometers per year, primarily due to flood control and channeling projects. Worldwide, half of all salt marshes and mangrove swamps have been cleared, drained, diked or filled.
Offshore, coral reefs, kelp forests, sea grass beds and other shallow water habitats are endangered by direct destruction and pollution from the land. Coral reefs, lining more than 100,000 kilometers of coast and harboring a large portion of the oceans' biological wealth, are of particular concern. The reefs are second only to tropical rain forests in density of unique species and recover slowly from damage.
Without close attention to the management and protection of coastal ecosystems, the destruction is bound to accelerate. Rural poverty, generating migrations to coasts - often to Third World mega-cities - is one major cause. In China, coastal population may be increasing by 10 percent per year, compared to the overall growth rate of 1.2 percent. Population density in these areas is already three times the national average, and this region accounts for 70 percent of the country's GNP.
Environmental assaults also come from inland. About half of all polluting nutrients come from inland. For example, farms contribute one-third and air pollution another one-quarter of the nitrogen pollution responsible for eutrophication, algal blooms and oxygen depletion of Chesapeake Bay. Once one of the most productive estuaries, the oyster catch has fallen from 20,000 tons in the 1950s to less than 3,000 tons in the late 1980s.
Air pollution contributes about one-third of pollutants to marine environments. Air is the primary route for heavy metals and volatile organic chemicals.

Global Implications

What happens to the coasts has effects that reach far beyond their local aquatic and human communities. Though they are among the most vulnerable of Earth's ecosystems, the coasts house biological processes and diversity that are essential to the health and stability of the biosphere as a whole.
The oceans, which are the largest ecosystems, rely disproportionately on the coasts for food. Although the coastal waters over continental shelves cover only 10 percent of the ocean surface, they account for 20 percent of the marine plant production. The energy captured in these waters' prolific plant growth feeds into the oceanic food chain, starting with small marine organisms such as copepods and other zooplankton, and moving out to sea with currents and migratory species. Unlike on land, animal life makes up the majority of biomass in the oceans, and its movement into the open ocean redistributes some of the disproportionate productivity of coastal waters.
This coastal productivity also helps to drive the oceans' "biological pump," the process by which the oceans help to regulate global climate. Scientists have found that the marine food chain moderates the atmospheric concentration of carbon dioxide, the primary heat-trapping gas. Carbon dioxide enters the churning upper layer of the oceans, where phytoplankton and other marine plants use it in photosynthesis to make simple sugars. While 90 percent of this carbon is recycled through the food chain, some falls into the deeper layers of the oceans as the detritus of decaying phytoplankton and other sea plants or animals. There, the carbon is stored in deep ocean currents that take about 1,000 years to bring it back to the surface as carbon dioxide.
The large amounts of biomass produced and consumed along the coasts, too, may play a major role in global warming. On one hand, some of the carbon dioxide captured by marine plants is stored in coastal sediments. On the other hand, some of the carbon trapped in organic matter flowing in from land is oxidized and re-released to the atmosphere. Scientists are still uncertain whether the coasts are a net source or sink of carbon. But either way, altering coastal processes is likely to have a global impact because of the sheer quantity of carbon pumped through this zone.
The high biological diversity of the coasts helps to stabilize these global systems. Organisms ranging from bacteria to great blue whales play key roles. Copepods, for instance, are minute crustaceans that eat phytoplankton and are thought to be the most numerous animals in the oceans. They fill a critical link between the primary producers and the rest of the marine food chain. If ecological conditions change in a way that no longer permits copepods to perform this function, their disappearance could have devastating consequences.
But there's another dimension, as well, to the extraordinary diversity of coastal organisms. About 90 percent of the history of life on earth has taken place in salt water, making the oceanic gene pool an invaluable resource. Its species are the descendants of the 3 to 3.5 billion years of evolution that predated the appearance of plant life on dry land some 450 million years ago. Therefore, many coastal species have no evolutionary counterparts on dry land. These unique species make irreplaceable contributions to food production, medicine, and scientific research.
A large proportion of these species are housed in coral reefs. Only the deep ocean floor, which covers half the earth's surface, is thought to contain more. Within coastal waters, a general rule of diversity is that shallow waters harbor more diversity than deeper waters, rocky areas more than sandy or muddy ones, and the tropics more than temperate or polar zones. Coral reefs - shallow, rocky, and tropical - are believed to contain the highest density of unique species in the oceans.
Researchers are increasingly turning to these coastal waters in their search for medical cures and unique compounds. They have derived anti-leukemia drugs from sea sponges, bone graft material from corals, diagnostic chemicals from red algae, and anti-infection compounds from shark skin. Because marine life is relatively unstudied compared to terrestrial life, the oceans and coasts are a vast new frontier for research.

Shoring up the sea

Under the current international regime, protecting the coastal zone is up to coastal nations. Nearly two decades ago, international negotiations over the Law of the Sea, a United Nations-mediated treaty on the management of the oceans, gave rise to international acceptance of the concept of a 200-nautical-mile coastal area - called the Exclusive Economic Zone (EEZ) - within which the coastal country has exclusive rights to the natural resources. By 1976, 60 countries had claimed EEZs of their own and the notion became an accepted part of customary oceans law.
The recent ratification of the Law of the Sea formalizes the EEZ construct and puts in force the treaty provisions that encourage coastal states to conserve and protect these waters. But the language is vague and probably unenforceable because of long-standing concerns over national sovereignty - the same issue that blocked international standards for coastal zone management at the 1992 Earth Summit in Rio de Janeiro. The delegates acknowledged the growing coastal crisis, but they shied away from infringing on national jurisdiction.
Of the three major threats to the coasts - coastal development, pollution from inland, and overfishing of coastal waters - it is development that warrants the highest priority for major changes in policy. The direct destruction and pollution of essential ecosystems is steadily undermining the coastal zone on every continent, and the surging of coastal populations means that these threats are worsening.
The single most effective change that could be made to slow the juggernaut of coastal development would be to eliminate subsidies such as government-sponsored insurance and funding for ocean-altering roads, dikes, and dams. The Netherlands, for instance, spends $400 million a year just to pump water and repair inland dikes, and new sea walls and dikes can cost hundreds of millions of dollars. These investments have come under domestic scrutiny, not only because they contribute to the loss of coastal habitat for the stork and other wetland-dependent species, but also because they may not be cost-effective. Some of the impounded agricultural land is often too wet to farm, and the Dutch don't need all of it because they are already producing more food than they can either use or sell abroad. As a result, expenditures on draining coastal land for farming can lead, absurdly, to still more expenditures on farm subsidies to cover excess production.
To save money and begin rehabilitating the coastal ecosystem, the Dutch government has made an extraordinary and courageous decision to return 150,000 hectares of farmland (15 percent of the total converted area) to rivers and estuaries over the next 25 years. Although the Dutch will continue diking and developing other parts of the coastal zone, this reversal reflects their growing concern over the degradation of their coasts.
In the early 1900s, the Dutch built a 30-kilometer-long earthen sea wall across the mouth of the Zuider Sea in the northwest to protect the impounded farmland in the estuary from flooding. The barrier against the sea completely altered the original ecosystem, turning the giant brackish water estuary into a fresh water lake, now known as Lake IJssel. The country has continued to pursue this strategy of "coastal defense," but recent projects have been more ecologically sensitive. For instance, rather than building a similar earthen sea wall across all of the estuaries in the rich coastal region of Zeeland in the southwest, the Dutch built mechanical sea walls that can be opened to allow relatively natural water flow, and closed in case of a strong coastal storm that threatens flooding.
As the Zeeland projects demonstrate, coastal development can be made less destructive. But the methods don't have to be high-tech engineering solutions. Natural buffer zones, for instance, can protect coastal habitat from nearby development. Wetlands trap toxins, pathogens, and excess nutrients and sediments as they move seaward, while also protecting coastal communities from coastal storms and sea surges. Coral reefs act as natural sea walls, reducing the erosive action of the ocean by absorbing the impact of waves.
Simple guidelines can make a significant difference. In Thailand's Ban Don Bay, for instance, the provincial government instituted building restrictions to protect the region's primary tourist attraction, the coral reefs. Developers now must build back from the beach and cannot use coral for construction material.
In Ecuador, which has lost 144,000 hectares of mangrove forests to shrimp ponds, the government is sponsoring a national program to manage coastal resources so that local communities can continue to profit from them without destroying them. Starting with a U.S. Agency for International Development pilot project, the Ecuadorean government has formed six special coastal management zones, with management committees composed of local and government people. In the case of the shrimp industry, which constitutes a sizable portion of Ecuador's exports and economy (nearly 80,000 metric tons of shrimp, worth almost $500 million in 1991), shrimp farmers were given special training on how to protect the coastal environment while maintaining their livelihoods.
Even if well-managed, however, coastal development could turn the world's coastlines into continuous strings of cities, farms, and resorts. Aside from the catastrophic ecological impacts, such an eventuality could take a heavy toll on those who live and invest there. As is becoming increasingly evident in places like the Eastern seaboard of the United States, coasts are dynamic. Portions are always eroding or shifting, and over the course of tens of thousands of years, changes in sea level can alternately expose and inundate the coastal zone. In the 10,000 years since the last ice age, the sea level has been rising as the result of melting ice and glaciers and thermal expansion of the oceans. Most of the world's low coasts continue to retreat due to the recent rate of sea level rise of 1 to 2 millimeters per year, or 10 to 20 centimeters per century.
With the increase in greenhouse gases and the threat of global warming, coastal living in the coming century will become more precarious. Sea level is projected to rise by 60 centimeters in the next 100 years, and storms are likely to grow stronger. Governments may need to consider restricting or even prohibiting further coastal development altogether.

Part I of this article was published in the Aug/Sep issue.